摘要
研究了采用多道搭接形式冷金属过渡(CMT)增材制造的TC4-DT合金试块不同区域的宏观、微观组织和晶体取向差异,及其对力学性能的影响。低倍组织观察表明,堆积试块底部由尺寸较小的柱状晶和等轴晶组成,随着沉积高度的增加,转变为粗大的等轴晶,层界线呈弧形并在搭接区交叠。堆积区高倍组织主要由编织状α板条组成,搭接线两侧为细编织状组织、粗大的α片层组织和粗编织状组织组成的混合组织。普通堆积区存在由{001}β//Z丝织构转变形成的α转变织构。搭接区由于热传导的复杂性,还存在由{001}β与Z方向呈22.5°~67.5°的丝织构转变而成的α转变织构。EBSD分析显示,搭接线处存在<0001>α//X方向的强织构,使得搭接线处柱面滑移和基面滑移Schmid因子均比较小,阻碍位错滑移,结合Hall-Petch关系分析表明,原始β晶界和搭接线是影响力学性能一致性的主要因素,在2种因素的共同作用下,各区域的平均有效位错滑移程呈现以下关系:搭接区<普通堆积区底部<普通堆积区顶部,导致不同区域屈服强度具有以下关系:搭接区>普通堆积区底部>普通堆积区顶部。
TC4-DT alloy is developed based on TC4 alloy, with medium strength and high damagetolerance, showing a great promise to be widely used in aerospace field. However, the traditional method to fabricate large and complicated parts has the problems of hot working difficulty, long processing cycle,low "buy-to-fly" ratio and high-cost. Additive manufacturing(AM) technology is a good alternative and has been used to manufacture titanium parts since year 2006. Compared to other AM technologies, cold metal transfer mode wire and arc additive manufacturing(CMT WAAM), as a kind of gas metal arc welding (GMAW) technology, has several advantages like simple structure, good spatial accessibility and high efficiency. In this study, a TC4-DT deposit was fabricated by CMT WAAM method. The macrostructure and microstructure, texture, and tensile properties in the overlapping zone and ordinary deposition zone were investigated and compared. The bottom of the ordinary deposition zone consisted of columnar and equiaxed prior β grains, and in higher zone the coarse equiaxed prior β grains were in the majority. The microstructure of the ordinary deposition zone was mainly characterized by basketweave α phase platelets. Microstructure of both sides of the overlapping line was characterized by a mixture of fine basketweave, lamellar and coarse basketweave α phase due to temperature gradient. Transformed α texture from {001}_β//Z silk texture existed in different zones, and the texture of overlapping zone was complicated due to the complexity of heat dissipation conditions, including transformed α texture and other complicated texture. EBSD results showed that there was a strong <0001>_α//X texture at the overlapping line, resulting in low Schmid factors for both prismatic slip and basal slip at the overlapping line, hindering the slip of dislocation. Combined with the Hall-Petch relationship, it was concluded that the prior β grain boundary and the overlapping line were main factors affecting the uniformity of mechanical properties.The average effective dislocation slip distances in different zones had the following relationship: overlapping zone<bottom of the ordinary deposition zone<top of the ordinary deposition zone, leading to different yield strengths in different zones of the ordinary deposition zone.
作者
杜子杰
李文渊
刘建荣
锁红波
王清江
DU Zijie;LI Wenyuan;LIU Jianrong;SUO Hongbo;WANG Qingjiang(School of Materials Science and Engineering,University of Science and Technology of China,Shenyang 110016,China;Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China;Qingdao JointX Intelligent Manufacturing Limited,Qingdao 266109,China)
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2020年第12期1667-1680,共14页
Acta Metallurgica Sinica
作者简介
杜子杰,男,1995年生,硕士;通讯作者:李文渊,wyli@imr.ac.cn,主要从事高温钛合金、增材制造的研究。
